The present invention generally relates to a device and method for detecting an imminent vehicular collision and providing improved safety restraint system response. More specifically, the present invention relates to a complete safety restraint system which uses a low-cost, low power, short-range radar sensing system and other suitable auxiliary sensors in conjunction with an electronic safety control unit to improve activation of various safety components such as air bags and seat belts.
Various technologies have been proposed to allow the sensing of an obstacle in the path of a vehicle. These prior technologies include infrared, lasers, ultrasonic and other traditional forms of radar. These prior technologies have generally been designed to provide obstacle detection at ranges up to several hundred feet for collision warning systems, intelligent cruise-control applications and automatic braking systems.
The primary purpose of this invention is to provide an improved safety restraint system using a low-power, low-cost predictive input to a safety restraint control unit. The radar sensor would determine range and trajectory, and predict the impact location and time of impact of the obstacle with the vehicle, and provide this information to the safety system electronic control unit. Depending on the type of obstacle discrimination desired, an auxiliary sensor such as an infrared detector, is used to provide additional information on the obstacle. Once an obstacle has been detected within the range capability of the radar sensors, tracking software is activated, whereupon velocity and trajectory computations are performed. As will be evident in the description that follows, this information can be utilized to provide an earlier discrimination decision on the relative severity of the impending impact than is possible with the reactive crash detection sensor systems in common use today, as well as used to calibrate the crash severity sensing system with significantly greater immunity to undesired restraint activation that can occur during rough road and abuse situations.
A first embodiment of the invention consists of a low-power radar transmitter/receiver with appropriately designed antennae located at each corner of the vehicle as illustrated in FIG. 1. Each corner antenna is designed to provide a beam coverage angle of approximately 270 degrees, and to allow appropriate packaging within the styling requirements of the vehicle body. This may require mounting the antennae inside of, for example, a lamp housing to provide desired appearance. As shown in FIG. 2, the beam pattern overlap of this antenna configuration permits the entire circumference of the vehicle to be within the beam pattern of at least four (4) radar units. The radar units are pulsed at a sufficiently high rate and for a long enough duration to provide a reliable echo of the obstacle to be determined. Adjacent radar units can be powered at slightly different frequencies, or they can be activated alternately within the given pulse frequency/duration limits to reduce interference between the sensors and to assure that the reflected pulse received by a specific sensor was actually transmitted by that same sensor. Similarly, for an obstacle to be classified as nonspurious, it must be tracked by at least two of the sensors for more than one measurement cycle. The velocity of the obstacle can then be calculated by triangulation knowing the distance between the sensors, the measured pulse return time from each of the two sensors, and the difference in obstacle distance from one measurement to the next. Alternately, the velocity of the obstacle can be determined through Doppler shifting of the radar signal if suitable sensor electronics are deemed appropriate for the application. These computations of obstacle approach can be performed in the central electronic safety system control unit, or in a dedicated electronic control unit designed specifically for the radar signal analysis. Once the range and approach velocity of the obstacle are known, the trajectory and impact location of the obstacle are calculated by straight-line extrapolation or other suitable methods. Should certain pre-determined thresholds for obstacle impact velocity and impact location be met, then the radar electronic control unit provides an output signal, either incremental or continuously varying, to the safety restraint control unit. This signal is then used by the safety restraint control unit to modify the activation of various restraint components.
Another embodiment of this invention incorporates a secondary predictive sensing system, such as an infrared transmitter/receiver, with the primary (radar) predictive sensing system for the purpose of better obstacle identification or discrimination. In this embodiment, the primary obstacle locating and tracking system locates and tracks the obstacle as described above. Once it is determined that there is a high likelihood of an impact of an obstacle with the vehicle and that velocity and trajectory values are within pre-determined thresholds, the electronic control system signals the auxiliary sensor to obtain additional information about the obstacle. This additional information may be, but is not limited to, an infrared profile of the obstacle to determine the likelihood of the obstacle being human to, for example, determine if external safety devices carried on the vehicle should be activated to provide improved pedestrian protection.
It is the object of this invention to provide an improved safety restraint control system that includes a predictive impact radar sensing system including: a radar electronic control unit, a central safety restraint system control unit, optional auxiliary sensors to improve the discrimination ability of the primary predictive sensing system, frontal air bags, seat belt pretensions, side air bags and other restraint components.
Accordingly, this invention comprises: a system for determining the presence, range, velocity and trajectory of an obstacle with a high probability of imminent impact with a vehicle, an optional sensing sub-system to improve discrimination ability of the primary predictive sensing system, an electronic safety control unit which determines the activation of various safety restraint components based on data generated either internal to the unit or supplied externally by other devices, safety restraint means, such as a system including a three point safety belt system having a pretensioner with or without slack take-up means and load-limiting means and various air bags for protecting the occupant during a crash.
Other objects and purposes of the invention will be clear from the following detailed description of the drawings: